PLATK XXV— Continued. 



Genus CiTRTIA, Dayman. 



Page 40. 



Cyrtia cyrtiniformis, H.ill and Whitfiekl. 



Fiffs. 26-28. Three views of a normal example ; ehowing the extei-nal characters. 



Fig-. 29. A cardinal view ; showing the great height of the area. X 2. 



Fig. 30. The central cardinal portion of the conjoined valves ; showing the dental plates of the pedicle- 

 valve, the cardinal process and socket-walls of the brachial valve. X 2. 



Fig. 31. The interior of a portion of the brachial valve ; showing the cardinal process, dental sockets and 

 socket-walls, and the subdivision of the muscular area. X 3. 



Fig. 32. A specimen, showing the crura, jugal processes and spiial cones. 

 Hamilton group. Hockford, Iowa. 



Genus SYRINGOTHYRIS, A. Winchell. 



rage 47. 



Syringothyris Hannibalensis, Swallow. 



Fig. 33. The exterior of a portion of the brachial valve. 



Fig. 34. A cardinal view of the pedicle-valve ; showing the dellhyrial callosity or canaliferous plate. 

 Fig. 35. The articulating apparatus of the brachial valve. X 2. 

 Choteau limestone. Pike cauntij, Missouri. 



